The "vast majority" of kids don't engage in that type of behavior, but for those who do the consequences can be embarrassing and long-lasting, Claus said.

In one of the Fargo cases, a caregiver for a juvenile found naked pictures that the girl had taken of herself and stored on her cell phone.

"Looking at the phone, she's got contacts for Facebook and stuff like that, so who knows who she sent it to," Shaw said. "They don't understand that when they're 15 years old that at 25 the picture's going to be on the Internet."

In another case, the mother of an 18-year-old found photos of his penis on his phone. The pictures had been sent to his 17-year-old girlfriend, Shaw said. The teens admitted to having sex, and no charges were sought, he said.

The latest case, reported to police on Aug. 20, involved an 18-year-old who sent nude photos of himself via cell phone to his underage girlfriend. That case remains under review, Shaw said.

Authorities struggle with how to enforce the law when dealing with such incidents, handling them on a case-by-case basis, Shaw said.

"We're going to have to adapt our laws, I think," he said.

"Right now, if an 18-year-old wants to have sex with a 17-year-old, that's OK," he added. "But as soon as he takes a picture of her, that's child pornography."

"There is a subjective part of it," Jacobson said. Before taking a case to court, police try to determine whether a jury would judge the action as criminal activity by reasonable standards, he said.

Claus said it's "probably unlikely" that police would charge a minor with disseminating child porn for sending pictures of himself or herself.

"But the fact is there's a great deal of danger in putting images of yourself out electronically," he said.

Fargo Public Schools is well aware of the problem, although no cases have been reported so far, spokesman Lowell Wolff said. Students aren't supposed to use cell phones in school, so it more than likely would happen off school grounds, he said.

"On the other hand, we're not so naive as to think that doesn't happen in school," he said.

Internet safety is part of the curriculum for students in grades three through eight, Wolff said. Those lessons also pertain to text messaging, especially when it comes to cyber-bullying, he said.

"Increasingly, as the line between cell phones and the Internet blurs, so too does the conduct we're talking about," he said.

Amy Arness, a mother of two teenagers and president of the Fargo Parent Teacher Association, said she wasn't aware of any local instances of students sending naked pictures via cell phones.

Arness said she occasionally will "go in and take a look" at the cell phones used by her daughter and son to see who they've been talking to and who's in their contact lists. She also reviews the monthly cell phone bill.

While cell phones help parents keep in touch with their kids, they also require extra effort in other ways, she said.

"You have to be a little bit more vigilant about touching base with each other," she said.

When a photo of a naked minor gets reported to police, investigators try to track down others who may have possession, Jacobson said.

The photos also are sent to the National Center for Missing & Exploited Children to be stored in a database, Shaw said. Victims are notified when their photo shows up in a criminal investigation.

Shaw said parents should treat their child's cell phone like they do their home computer, because both have the capability to send and receive photos and videos.

"The same risks are there," he said. "They could still have ... a predator on there."

Parents can limit text messaging and Internet service on their child's phone through their cellular provider, Shaw said. If the child grumbles too much about it, parents can buy software that allows photos taken on cell phones to be downloaded to a computer and then e-mailed, he said.

"(Then) you don't have the instantaneous thing to worry about," he said.

Claus said it behooves parents to know what their children are doing not only on the computer, but also on their cell phones.

"Because a moment of indiscretion in a young person's life may lead to those photos and those things being out there forever," he said.

Nude photo cases seen nationally

An Associated Press article in June told of several instances across the country in which nude photos of teens were sent electronically:

- In Santa Fe, Texas, school administrators confiscated dozens of cell phones from students in May after nude photos of two junior high girls began circulating. The girls sent the photos to their boyfriends, who forwarded them to others.

- In La Crosse, Wis., a 17-year-old boy was charged with child pornography, sexual exploitation of a child and defamation for allegedly posting nude photos of his

16-year-old girlfriend on his MySpace page. Authorities said the girl took the pictures with her cell phone at her mother's home and e-mailed them to her boyfriend.

- In suburban Syracuse, N.Y., several teenage girls sent naked pictures on their phones to their boyfriends, only to learn that another boy had collected them from the Web and was trying to sell a DVD of them.